Geminal diazides

Alkoxyalkynes are an exception, but unfortunately they undergo further additions to yield geminal diazides as the only product (equation 187).266... 

Table 30 Synthesis of tetrazoles from ketones and SiCI4-NaN3 via geminal diazide 520 <1995TL7337>...

The data published before 1996 on the conversion of ketones (aldehydes) into 1,5-disubstituted tetrazoles 5 through geminal diazides 520 have been collected and systematized <2004SOS( 13)861 > (Scheme 74 Table 31). 

The formation of tetrazole derivatives from geminal diazides has been observed and correctly interpreted already in 1931 [31CB1555], The thermal decomposition of dimethyl diazidomalonate was reinvestigated by R. M Moriaty [85JOC3710] after our short report in 1984 [84CC338],... 

The action of concentrated sulfuric acid at 0 °C on the geminal diazide 2 gives in high yield (> 90 %) the N-oxamoyl anthranilic acid 14 [72TH000], This compound can be further hydrolyzed to anthranilic acid 15 or converted into the ester 16. N-Alkyl derivatives of 2 behave in a similar manner cf. the conversion of 18 to 19. The latter compound may be easily degradated to 1,2,3,4-tetrahydroquinoline-l-carboxylic acid in the same way. Only the biphenyl derivative of 2 reacts differently and affords acridone 17 in 65 % yield. The cleavage of the C-3 - C-4 bond in these reactions is again noteworthy. 

To explore further the structural requirements for this unexpected nitrile formation (51 — 52) the reaction of the 1-methyl derivative 56 with sodium azide was examined. In this case the diazido derivative 57 was obtained instead of the nitrile 58. In a control experiment the nitrile 58 was also prepared by methylation of 52 with trimethyl phosphate in the presence of potassium carbonate. 58 reacted in analogy to 52 with sodium azide to furnish the tetrazole 59. Attempted decomposition of the geminal diazide 57 in refluxing DMF failed to give the tetrazole 59 (which is very surprising in view of the easy conversion of 38 to 39) [90LA505],... 

In addition, the reaction was extended to the 4-unsubstituted tetrahydro-pyrimidines 60. Here the same reaction pattern as before was observed The 1-unsubstituted derivative led to the 6-cyanopyrimidine 61, whereas the 1-methyl derivative afforded the geminal diazide 62 [90LA505],... 

In addition to the thermal decomposition the photochemical reaction of geminal diazide 62 was also studied. Irradiation of an acetone solution of 62 under an inert gas atmosphere afforded a complex mixture of products which could not be separated or identified. However, if the reaction was carried out in the presence of oxygen the uracil derivative 66 was obtained in 48 % yield. Surprisingly, in addition to the oxidation of the CH2 group, the 6-diazidomethyl function was completely lost during the reation [91JCS(P1)1342]. At the present time no mechanistic explanation for this unusual behavior can be presented. On the other hand, photooxidation of compound 63 leads straightforward to compound 67 [91 JCS(P1)1342],... 

Progress in Heterocyclic Chemistry (PHC) Volume 8 reviews critically the heterocyclic literature published mainly in 1995. The first two chapters are review articles. Chapter 1 by T. Kappe deals with Geminal Diazides of Heterocycles, and Chapter 2 by M. Sibi and J. Ji provides extensive coverage of the important emerging area of Radical Methods in the Synthesis of Heterocyclic Compounds. The unusual length of the latter contribution attests to the rising power of this methodology in heterocycle construction. 

An interesting reaction was discovered by Moriarty in the photolysis of the geminal diazide, dimethyl diazidomalonate (28) Irra-... 

An attempt to prepare the geminal diazide 103 from 9-(dichloro-methylene)fluorene (102) and sodium azide at room temperature resulted in the formation of 9-azido-9-fluorenecarbonitrile (104) This product can be explained as arising from the diazide 103 by loss of molecular nitrogen from one azido group, followed by reorganization of the remaining atoms. 

On the other hand, when a mixture of 1,2-dimethylcyclobutene, iodine monochloride and sodium azide in acetonitrile was stirred overnight, an unexpected geminal diazide 5 was formed... 

Photodecomposition of carbohydrate-derived geminal diazides appears to proceed via intermediate carbenes, ° whereas irradiation of the diazidomethylpyrimidine (70) in acetone affords the uracil carboxylate (71), but only in the presence of oxygen. 

The Schmidt transformation of ketones to IH-tetrazoles (predominantly isomer A) with sodium azide-titanium tetrachloride was rmorted by Suzuki el at [93S1218]. Mechanistically, a geminal diazide undergoes loss of nitrogen to form an a-azidonitrene which undergoes a [l,2]-substituent shift to lead to preferential formation of isomer A. However, in a few cases [R = QH5 and = 4-Me(X 6H4. = CgHs and R = CH3]... 

DHPM 308 (R = R = H) with nucleophiles gave C-6 substituted 315 (Scheme 121). With sodium azide, C-6 azidomethyl 316 was obtained, which with Pd(0) and a hydrogen acceptor such as diphenylacetylene furnished C-6 cyano 317, also formed from 309 with sodium azide in HMPT. Sodium azide with 317 furnished tetrazole 319. The N-1 methyl of 309 (R = Me, R = H) with sodium azide gave geminal diazide 318 (Scheme 121) (90LA505). 

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